Activated carbons with molecular sieve membranes and their use as adsorbents in smoking articles

ABSTRACT

A composite for use in smoking articles such as cigarettes is described comprising a zeolite membrane coated upon an activated carbon-containing substrate. The substrate may be a fiber, fabric, particle, granule or monolith. The composite is prepared by contacting zeolite precursors with the substrate and hydrothermally synthesizing the membrane upon the substrate. The substrate may be pretreated to provide activation sites for adhesion and growth of the membrane. By selection of the zeolite components, the composite may be tailored to selectively remove constituents of tobacco smoke while simultaneously controlling access to the substrate thereby prolonging the shelf life of the activated carbons.

BACKGROUND

Various activated carbon materials have been employed as sorbents insmoking articles to remove or reduce smoke constituents. Activatedcarbons are useful sorbents and have a large capacity; however, theylack selectivity. While they are effective in removing targetedconstituents from tobacco smoke, they also may remove volatileconstituents which contribute to flavor, aroma and other desirableattributes. Further, activated carbon in a cigarette filter may berapidly inactivated during storage by the adsorption of volatilecompounds, or by contact with various constituents of mainstream smoke.

Zeolite-type molecular sieves have also been used in smoking articles toselectively remove constituents of tobacco smoke. Zeolite molecularsieve sorbents are capable of selectively removing one or more targetedconstituents of mainstream smoke. However, zeolites have minimalcapacities and are quickly exhausted before removing a significantamount of the targeted constituent.

There is interest in a filter system for use in smoking articles whichcan readily be manufactured in various shapes from commerciallyavailable activated carbons and zeolite materials and can be tailored toproduce components which selectively remove or reduce the concentrationof various smoke constituents while retaining desirable flavorconstituents and having an extended shelf life.

SUMMARY

A smoking article is provided which includes tobacco and a filter systemcomprising a composite composed of an activated carbon substrate and azeolite-type membrane coated thereon. Also provided is a filter system,a method of making smoking articles containing said filter system and amethod of selectively removing targeted constituents from tobacco smoke.

In one embodiment, a filter is prepared containing a composite made bythe deposition of a molecular sieve membrane directly onto acarbon-containing substrate by hydrothermal synthesis of a givenmolecular sieve. Pre-treatment of the substrate may be desirable toachieve optimum adhesion and growth of the membrane on the substrate.

In another embodiment, cigarettes are prepared which contain tobacco andthe filter mentioned above. A preferred smoking article is a traditionalor non-traditional cigarette. The aforementioned composite preferably isincorporated into a filter of a cigarette.

Another embodiment relates to a method of making a filter cigarette,comprising: (i) providing a cut filler to a cigarette making machine andforming a tobacco column; (ii) placing a paper wrapper around thetobacco column and forming a tobacco rod; (iii) attaching a cigarettefilter comprising the composite described above to the tobacco rod toform the cigarette.

In another embodiment, a method is provided of treating mainstream smokeof a smoking article to preferentially remove one or more targetedconstituents from mainstream smoke by contacting the mainstream smokewith a composite as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a cigarette wherein folded paper containing acomposite described above is inserted into a hollow portion of a tubularfilter element of the cigarette.

FIG. 2 is a view of another embodiment wherein a composite as describedabove is incorporated in folded paper and inserted into a hollow portionof a first free-flow sleeve of a tubular filter element next to a secondfree-flow sleeve.

FIG. 3 is a view of another embodiment wherein a composite as describedabove is incorporated in a plug-space-plug filter element.

FIG. 4 is a view of another embodiment wherein a composite isincorporated in a three-piece filter element having three plugs.

FIG. 5 is a view of another embodiment wherein a composite isincorporated in a four-piece filter element having a plug-space-plugarrangement and a hollow sleeve.

FIG. 6 is a view of still another embodiment wherein a composite isincorporated in a three-part filter element having two plugs and ahollow sleeve.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Cigarette filters and smoking articles are provided preferablycontaining a porous composite comprising an activated carbon substrateand a zeolite molecular sieve membrane coated thereon and capable ofselectively removing selected constituents from mainstream smoke.Methods for making such cigarette filters and smoking articles, as wellas a method of treating mainstream smoke, are also provided.

The term “sorption” denotes filtration by adsorption and/or absorptionand is intended to encompass interactions on the outer surface of asorbent, as well as interactions within the pores and channels thereof.A “sorbent” is a substance that has the ability to condense or holdmolecules of other substances on its surface and/or the ability to takeup other substances, i.e., through penetration of the other substancesinto its inner structure or into its pores. The term “sorbent” as usedherein refers to either an adsorbent, an absorbent, or a substance thatcan function as both an adsorbent and an absorbent.

The term “remove” as used herein refers to adsorption and/or absorptionof at least some portion of a selected constituent of mainstream tobaccosmoke.

The term “mainstream smoke” includes the mixture of gases andaerosolized condensed matter which passes down a tobacco column andissues through the filter end, i.e., the amount of smoke issuing ordrawn from the mouth end of a smoking article such as a cigarette duringsmoking. The mainstream smoke contains air that is drawn in through boththe lit or heated region of the smoking article, as well as through thepaper wrapper, and through any ventilation perforations that may bepresent.

Smoking articles, such as cigarettes, cigarillos and cigars, as well asnon-traditional cigarettes, are provided. Non-traditional cigarettesinclude, for example, smoking articles which include combustible heatsources such as that shown in commonly assigned, U.S. Pat. No.4,966,171, and cigarettes for electrical smoking systems as described incommonly-assigned U.S. Pat. Nos. 6,026,820; 5,988,176; 5,915,387; and5,499,636.

The substrate portion of the aforementioned composite comprises anactivated carbon. Activated forms of carbon generally have strongphysical sorption forces, and high volumes of sorbing porosity. Theactivated carbon could be manufactured by any suitable method. Suchmethods include the carbonization of coconut husk, coal, wood, pitch,cellulose fibers, or polymer fibers, for example. Carbonization isusually carried out at high temperatures, i.e., 200-1000° C. in an inertatmosphere, followed by activation. The activated carbon used as thecomposite substrate could be in the form of carbon granules, beads,powder, fiber, fabric or shaped monoliths. The substrate could also bean admixture of carbon and an inorganic material. Suitable inorganicmaterials may comprise porous and/or catalytically active metalcompounds such as oxides, hydroxides, silicates and phosphates.

Carbon-containing materials suitable as substrates may have adistribution of micropores, mesopores and macropores. The term“microporous” generally refers to such materials having pore sizes ofabout 20 Å or less while the term “mesoporous” generally refers to suchmaterials with pore sizes of about 20 to 500 Å. “Macroporous” materialshave pore sizes above about 500 Å. The relative amounts of micropores,mesopores and macropores in the carbon-containing substrate will dependupon the selected constituents from mainstream tobacco smoke that are tobe targeted and removed. Thus, the pore sizes and pore distribution canbe adjusted accordingly as needed for a certain application.

Another material in the filter system is a molecular sieve zeolitemembrane. The term “molecular sieve” as used herein refers to a porousstructure composed of an inorganic silicate material. Zeolites havechannels or pores of uniform, molecular sized dimensions. There are manyknown unique zeolite structures having different sized and shapedchannels or pores. The size and shape of the channels or pores cansignificantly affect the properties of these materials with regard toadsorption and separation characteristics. Zeolites can be used toseparate molecules by size and shape possibly related to the orientationof the molecules in the channels or pores, and/or by differences instrength of sorption. By using one or more zeolites having channels orpores larger than selected constituents of mainstream smoke, onlyselected molecules that are small enough to pass through the pores ofthe molecular sieve material are able to enter the cavities and besorbed by the zeolite.

Zeolite-type molecular sieves which are useful in the composites includecrystalline aluminosilicates, silicoaluminophosphates (AlPO/SAPO) andmesoporous molecular sieves such as MCM-41, MCM-48 and SBA-15. Thisfamily of materials contains regular arrays of uniformly-sized channelsand tunable internal active sites, and admits molecules below a certainsize into their internal space which makes them useful as catalysts andsorbents where selectivity is critical. Microporous and mesoporousmolecular sieves are preferred. They are selected for use in the filtercomposites based on the particular constituent or constituents to beremoved from the mainstream smoke.

The term “microporous molecular sieves” generally refers to molecularsieve materials having pore sizes of about 20 Å or less. The term“mesoporous molecular sieves” generally refers to such materials withpore sizes of about 20 to 500 Å. Materials with pore sizes of about 500Å or larger may be referred to as “macroporous molecular sieves.”

The composite preferably is prepared by a hydrothermal synthesistechnique using zeolite precursor materials which form a coated membraneon the substrate. The hydrothermal synthesis of various zeolites can beaccomplished by any techniques which would generate in situ a zeolitemembrane on the carbon-containing substrate. Methods for the preparationof zeolite membranes on activated porous carbon monoliths and porouscarbon membranes are disclosed in the following articles: “Preparationof hollow-fibre composite carbon-zeolite membranes,” Smith, S. P. J.;Linkov, V. M; Sanderson, R. D.; Petrik, L. F.; O'Connor, C. T.; Keiser,K., Microporous Materials, 1995, 4, pp. 385-390; “Preparation of an MFIzeolite coating on activated carbon,” van der Vaart, R.; Bosch, H.;Keizer, K.; Reith, T., Microporous Materials, 1997, 9, pp. 203-207, theentire disclosures of both articles incorporated herein in theirentirety. In general, the substrates are contacted with the zeoliteprecursors and a hydrothermal synthesis conducted whereby the zeolitemembrane is coated upon and/or into the pores of the substrate. If thecarbon-containing substrate has not been activated before synthesis ofthe zeolite membrane, known activation techniques may be employed toremove volatiles and produce the final activated composite. The productis a composite filter system composed of a porous substrate of activatedcarbon having a zeolite membrane coated uniformly upon the surface andwithin the pores of the substrate.

In the hydrothermal synthesis of crystalline aluminosilicates, sodiumhydroxide may be used as the alkaline source. Sodium aluminate (NaAlO₂),aluminum nitrate (Al(NO₃)₃9H₂O), aluminum sulfate (Al₂(SO₄)₃18H₂O),aluminum chloride (AlCl₃6H₂O), aluminum hydroxide (Al(OH)₃), aluminumalkoxide and alumina gel, etc. can be used as the source of alumina.Colloidal silica, fumed silica, water glass (sodium silicate aqueoussolution), silica gel, etc. can be used as the silica source.

The factors affecting crystallization of aluminosilicate include thesource of silica, the mole ratio of silica vs. alumina, pH, reactiontemperature, reaction time, degree of aging in room temperature,presence of stirring, etc. The morphology and nature of zeolite producedare directly linked to these variations.

An example of a method of preparing a molecular sieve compound isdescribed in U.S. Pat. No. 6,117,810, the entire disclosure of which isincorporated herein by reference. A sodium aluminate solution is made byadding a source of alumina to sodium hydroxide solution and stirring forabout 20 to 60 minutes at about 70 to 120° C. to dissolve completely.The concentration of sodium hydroxide in solution is about 20 to 50 wt.%, especially about 30 to 40 wt. %. A sodium silicate composition isproduced by stirring the sodium hydroxide solution and the silica sourceat a temperature of about 25° to 70° C. Thereafter, the sodium aluminatesolution is admixed with a sodium silicate composition in SiO₂/Al₂O₃mole ratios of about 2.0 to 40.0, Na₂O/SiO₂ mole ratios of about 0.4 to2.0 and H₂O/Na₂O mole ratios of about 15.0 to 70.0. Gelation is broughtabout by homogeneously stirring.

Following gelation, the gel composition is deposited onto and into thepores of the activated carbon substrate. In the above process, if themole ratio of SiO₂/Al₂O₃ is under 2.0, some of the alumina componentremains in the final product. If the mole ratio is greater than 40,crystallization of the zeolite becomes difficult. If the mole ratio ofNa₂O/SiO₂ is under 0.4, the activity of the silica component is low andit is slowly converted into zeolite. If the mole ratio is more than 2.0,a crystalline aluminosilicate is produced having a very low activity.

If the mole ratio of H₂O/Na₂O is under 15, alkalinity in solution is sohigh that side reactions can easily occur. If the ratio is more than70.0, higher pressures and temperatures are required for the synthesisreaction.

The reaction mixture is allowed to age for about 2 to 96 hours at about25 to 60° C. and crystallized at about 70 to 120° C., preferably at 80to 100° C., and most preferably at 90 to 100° C. for 2 to 4 hours.

Upon completion of crystallization, the slurry phase is separated, thefinal product washed with water, and dried for about 4 to 12 hours atabout 100 to 120° C. to provide the molecular sieve compound.

Preferred complex molecular sieve compounds produced are composed ofmicroporous zeolites such as A, ZSM-5, X or Y type finely distributedonto the surfaces of the activated carbon. Therefore, the compositeshave both hydrophilic and hydrophobic adsorption properties derived fromthe activated carbon and zeolite.

To facilitate adhesion and growth of the zeolite membrane on thecarbon-containing substrate, it may be desirable to pretreat thesubstrate to provide sufficient nucleation sites. Preferably, silanesare applied to the substrate followed by a heat treatment preferably inan oxidizing atmosphere. Suitable silanes include alkoxysilanes such astetraethoxysilane. Alternatively, hydrophilic clays such as bentoniteand montmorillonite may be admixed with the carbon-containing materialbefore, during or after preparation of the substrate material.Preferably, the carbon-containing substrate includes activated carbon.As indicated above, if the substrate is not activated beforehand, it maybe activated after deposition of the zeolite membrane such as by heatingthe composite which removes various volatiles used in the synthesis ofthe membrane while activating the substrate.

In a preferred embodiment, the composite is located in a filter portionof a cigarette. Typically, about 10 mg to about 300 mg of the compositecan be used in a cigarette filter. For example, amounts such as at leastabout 20, 30, 50, 75, 100, 150, 200, or 250 mg of the composite can beused in the cigarette filter.

Various filter constructions may be used to locate the composite.Exemplary filter structures that can be used include, but are notlimited to, a mono filter, a dual filter, a triple filter, a cavityfilter, a recessed filter or a free-flow filter. Mono filters typicallycontain cellulose acetate tow or cellulose paper materials. Dual filterstypically comprise a cellulose acetate mouthpiece filter plug and asecond, different filter plug or segment. The composite is preferablylocated closer to the smoking material or tobacco side of a cigarette.The length and pressure drop of the two segments of the dual filter canbe adjusted to provide optimal adsorption, while maintaining acceptabledraw resistance.

Triple filters can include mouth and smoking material or tobacco sidesegments, and a middle segment comprising a material or paper. Theaforementioned composite can be provided in the middle segment. Cavityfilters typically include two segments, e.g., acetate-acetate,acetate-paper or paper-paper, separated by a cavity. The composite canpreferably be provided in the cavity. Recessed filters include an opencavity on the mouth side, and the composite can be incorporated into theplug material. The filters may also optionally be ventilated, and/orcomprise additional sorbents (such as activated carbon, charcoal ormagnesium silicate), catalysts, flavorants or other additives.

FIG. 1 illustrates a cigarette 2 having a tobacco rod 4, a filterportion 6, and a mouthpiece filter plug 8. The composite can be loadedonto folded paper 10 inserted into a hollow cavity such as the interiorof a free-flow sleeve 12 forming part of the filter portion 6.

FIG. 2 shows a cigarette 2 having a tobacco rod 4 and a filter portion6, wherein the folded paper 10 is located in the hollow cavity of afirst free-flow sleeve 13 located between the mouthpiece filter 8 and asecond free-flow sleeve 15. The paper 10 can be used in forms other thanas a folded sheet. For instance, the paper 10 can be deployed as one ormore individual strips, a wound roll, etc. In whichever form, a desiredamount of the composite can be provided in the cigarette filter portionby adjusting the amount per unit area of the paper and/or the total areaof coated paper employed in the filter (e.g., higher amounts ofcomposite can be provided simply by using larger pieces of coatedpaper). In the cigarettes shown in FIGS. 1 and 2, the tobacco rod 4 andthe filter portion 6 are joined together with tipping paper 14. In bothcigarettes, the filter portion 6 may be held together by filter overwrap11.

The composite can be incorporated into the filter paper in a number ofways. For examples, particles or powders of the aforementionedcomposites can be mixed with water to form a slurry. The slurry can thenbe coated onto preformed filter paper and allowed to dry. The filterpaper can then be incorporated into the filter portion of a cigarette ina manner shown in FIGS. 1 and 2. Alternatively, the dried paper can bewrapped into a plug shape and inserted into a filter portion of thecigarette. For example, the paper can be wrapped into a plug shape andinserted as a plug into the interior of a free-flow filter element suchas a polypropylene or cellulose acetate sleeve. In another arrangement,the paper can comprise an inner liner of such a free-flow filterelement.

Alternatively, the composite may be added to filter paper during thepaper-making process. For example, the composite can be mixed with bulkcellulose to form a cellulose pulp mixture. The mixture can be thenformed into filter paper.

In another embodiment, the aforementioned composite may be incorporatedinto the fibrous material of the cigarette filter portion itself. Suchfilter materials include, but are not limited to, fibrous filtermaterials including paper, cellulose acetate fibers, and polypropylenefibers. This embodiment is illustrated in FIG. 3, which shows acigarette 2 comprised of a tobacco rod 4 and a filter portion 6 in theform of a plug-space-plug filter having a mouthpiece filter 8, a plug16, and a space 18. The plug 16 can comprise a tube or solid piece ofmaterial such as polypropylene or cellulose acetate fibers. The tobaccorod 4 and the filter portion 6 are joined together with tipping paper14. The filter portion 6 may include a filter overwrap 11. The filteroverwrap 11 containing traditional fibrous filter material and thecomposite can be incorporated in or on the filter overwrap 11 such as bybeing coated thereon. Alternatively, the composite can be incorporatedin the mouthpiece filter 8, in the plug 16, and/or in the space 18.Moreover, the composite can be incorporated in any element of the filterportion of a cigarette. For example, the filter portion may consist onlyof the mouthpiece filter 8 and the composite can be incorporated in themouthpiece filter 8 and/or in the tipping paper 14.

FIG. 4 shows a cigarette 2 comprised of a tobacco rod 4 and filterportion 6. This arrangement is similar to that of FIG. 3 except thespace 18 is filled with granules of composite or a plug 15 made ofmaterial such as fibrous polypropylene or cellulose acetate containingthe composite. As in a previous embodiment, the plug 16 can be hollow orsolid and the tobacco rod 4 and filter portion 6 are joined togetherwith tipping paper 14. There is also a filter overwrap 11.

FIG. 5 shows a cigarette 2 comprised of a tobacco rod 4 and a filterportion 6 wherein the filter portion 6 includes a mouthpiece filter 8, afilter overwrap 11, tipping paper 14 to join the tobacco rod 4 andfilter portion 6, a space 18, a plug 16, and a hollow sleeve 20. Thecomposite can be incorporated into one or more elements of the filterportion 6. For instance, the composite can be incorporated into thesleeve 20 or granules of the composite can be filled into the spacewithin the sleeve 20. If desired, the plug 16 and sleeve 20 can be madeof material such as fibrous polypropylene or cellulose acetatecontaining the composite. As in the previous embodiment, the plug 16 canbe hollow or solid.

FIG. 6 shows a further modification of the filter portion 6. In FIG. 6,cigarette 2 is comprised of a tobacco rod 4 and filter portion 6. Thefilter portion 6 includes a mouthpiece filter 8, a filter overwrap 11, aplug 22, and a sleeve 20. The composite can be incorporated in one ormore of these filter elements. The plug 22 can be solid or hollow. Thetobacco rod 4 and filter portion 6 are joined together by tipping paper14.

Various techniques can be used to apply the composite to filter fibersor other substrate supports. For example, the composite can be added tothe filter fibers before they are formed into a filter cartridge, e.g.,a tip for a cigarette. The composite can be added to the filter fibers,for example, in the form of a dry powder or a slurry. If the compositeis applied in the form of a slurry, the fibers are allowed to dry beforethey are formed into a filter cartridge.

In another embodiment, the composite is employed in a hollow portion ofa cigarette filter. For example, some cigarette filters have aplug/space/plug configuration in which the plugs comprise a fibrousfilter material and the space is simply a void between the two filterplugs. That void can be filled with the aforementioned composite. Anexample of this embodiment is shown in FIG. 3. The composite can be ingranular form or can be loaded onto a suitable support such as a fiberor thread.

As explained above, composite can be incorporated in various supportmaterials. When the composite is used in filter paper, the particles mayhave an average particle diameter of about 5 to 100 μm, preferably about10 to 50 μm. When the composite is used in filter fibers or othermechanical supports, larger particles may be used. Such particlespreferably have a mesh size from about 25 to 60, and more preferablyfrom about 35 to 60 mesh.

The amount of composite employed in the cigarette filter by way ofincorporation on a suitable support such as filter paper and/or filterfibers depends on the amount of constituents in the tobacco smoke andthe amount of constituents desired to be removed. As an example, thefilter paper and the filter fibers may contain from 10% to 50% by weightof the composite.

One embodiment relates to a method of making a filter. The methodcomprises incorporating the aforementioned composite into a cigarettefilter. Most filters contain four main components: filter tow,plasticizer, plug wrap and adhesive. Often the filter tow comprises abundle of cellulose acetate fibers or papers, that are bound togetherusing the plasticizer, which acts as a hardening agent. The filter iscontained in the plug wrap, usually a paper wrapper, which is securedusing an adhesive. Any conventional or modified method of makingcigarette filters may be used to incorporate the composite.

Another embodiment relates to methods for making cigarettes. Forexample, the method comprises: (i) providing a cut filler to a cigarettemaking machine to form a tobacco rod; (ii) placing a paper wrapperaround the tobacco rod; and (iii) attaching a cigarette filterincorporating a composite to the tobacco rod to form the cigarette.

The composites may be used to prepare impregnated fibers. Particles orpowders of the composite are first mechanically mixed with the fiber ina closed volume. The resulting impregnated fibers will thus have aLoading Factor (LF), which term is defined as the ratio of the weight ofmaterial in the fiber micro cavities divided by the weight of the fiberitself. The Loading Factor may be expressed as a percentage or as adecimal number.

The Loading Factor may vary between about 1% and about 150%. Morepreferably, the Loading Factor is between about 20% and about 80%, e.g.,the Loading Factor can be about 40-60%. The fibers that are impregnatedwith the composite are formed into a cylindrical segment which isinserted in the space of a cigarette with a plug/space/plug filterconfiguration. Preferably, the segment is packed to a density to achievea desired resistance to draw and contains an amount of the compositeeffective to filter out the selected smoke gas phase constituents.Tipping paper attaches the tobacco to the filter rod.

Activated carbons and zeolite-type molecular sieves when combinedtogether can produce composite materials with tailored sorption capacityand selectivity for application in smoking articles to selectivelyreduce targeted smoke constituents. The composite can be provided with asurface area effective to preferentially sorb selected constituents fromcigarette smoke. While surface area is inversely proportional toparticle size, sorbents having small particle size may pack together toodensely to permit mainstream smoke to flow through the filter duringsmoking. If particle size is too large, there will be less than desiredsurface area. Therefore, these factors should be considered inmanufacturing a composite having a particular particle size.

The zeolite and activated carbon used in making the composite may bechosen to target selected constituents in mainstream smoke, whileprolonging the shelf life of the activated carbon during storage ofsmoking articles containing the composite. The selection of startingmaterials permits the preferential removal of one or more selectedconstituents from mainstream smoke, while retaining other constituents,such as those relating to flavor. For example, smoke substituentsrelating to flavor of large size and/or molecular weight can passthrough the filter to a greater extent than smaller smoke substituents,such as light gases, various aldehydes or other small molecules whichmay be targeted for removal. The selectivity of the composite can befine tuned, particularly by the selection of zeolites and activatedcarbons as well as the choice of particle sizes and pore sizes. Mixturesof molecular sieves with varying compositions and geometries can beemployed to tailor the removal of selected constituents of tobacco smokewhile controlling access to the pores of the activated carbon substrate.

Selected constituents of mainstream smoke may be removed by thecomposite through one or more mechanisms such as molecular sieving, ionexchange, hydrophobic interactions, chelation, and/or chemical binding.The selected constituents of mainstream smoke that are removedpreferably are composed of at least one of a hydrocarbon, a polarorganic and/or non-polar organic compound. Preferably, the selectedconstituent of mainstream smoke that is removed is an aldehyde, ketone,diene or aromatic compound. Specific constituents which may be removedinclude carbon monoxide, 1,3-butadiene, isoprene, acrolein,acrylonitrile, hydrogen cyanide, o-toluidine, 2-naphthylamine, nitrogenoxide, benzene, phenol, and/or catechol. More preferably, theconstituent is an aldehyde or diene.

Variations and modifications of the foregoing embodiments will beapparent to those skilled in the art. Such variations and modificationsare to be considered within the purview and scope of the claims appendedhereto.

1. A smoking article comprising tobacco and a filter componentcomprising a composite comprising at least one activatedcarbon-containing substrate coated with at least one zeolite molecularsieve layer.
 2. The smoking article of claim 1, wherein said substratecomprises a fiber, fabric, particle, granule or monolith, and thezeolite comprises a crystalline alumino-silicate, asilicoaluminophosphate or a micro- or meso-porous molecular sieve. 3.The smoking article of claim 2, wherein the zeolite comprises amolecular sieve selected from ZSM-5, X, Y or A type zeolites.
 4. Thesmoking article of claim 1, wherein the article is a cigarette.
 5. Thesmoking article of claim 1, wherein the substrate is pretreated toprovide nucleation sites.
 6. The smoking article of claim 5, wherein thepretreatment comprises reaction with a silane.
 7. The smoking article ofclaim 1, wherein the activated carbon of the substrate has adistribution of micropores, mesopores and macropores.
 8. The smokingarticle of claim 4, wherein the filter component is a mono filter, adual filter, a triple filter, a cavity filter, a recessed filter or afree-flow filter, the filter component comprises cellulose acetate tow,cellulose paper, polypropylene fiber or combinations thereof, and thecomposite is incorporated into at least one cigarette filter partselected from a shaped paper inset, a plug, a space, cigarette filterpaper or a free-flow sleeve.
 9. A smoking article comprising a filtercomponent composed of a composite comprising at least one activatedporous carbon substrate and at least one zeolite molecular sievemembrane coated on the surface of and/or in the pores of the substrate.10. The smoking article of claim 9, wherein said carbon substrate ispretreated to provide nucleation sites.
 11. The smoking article of claim10, wherein pretreatment comprises reaction with a silane.
 12. Thesmoking article of claim 9 comprising tobacco cut filler, cigarettepaper and cigarette filter material, wherein the a composite is capableof selectively removing constituents from cigarette smoke, and whereinthe composite is prepared by hydrothermally synthesizing a zeolitemolecular sieve layer on said substrate.
 13. The smoking article ofclaim 12, wherein said article is a cigarette.
 14. A method of treatingcigarette smoke produced by the cigarette of claim 4, comprisinglighting the cigarette to form tobacco smoke and drawing the tobaccosmoke through the cigarette, wherein the composite reduces the amount ofselected constituents in the tobacco smoke, and wherein the composite islocated in a filter component of the cigarette.
 15. The cigaretteaccording to claim 13 comprising tobacco and a filter element, whereinthe filter element includes the composite comprising an activated porouscarbon substrate having a zeolite molecular sieve membrane coated uponand within the pores of the substrate, wherein the carbon substratecomprises a fiber, fabric, particle, granule or monolith.
 16. Thecigarette of claim 15, wherein the carbon substrate has been pretreatedwith a silane to provide nucleation sites.
 17. A method of manufacturinga cigarette filter, comprising incorporating into a cigarette filter acomposite comprising a porous activated carbon-containing substrate anda zeolite molecular sieve membrane coated upon and within the poresthereof, the composite being loaded on a support, or incorporated in asupport, or incorporated with a support, in a plug-space-plugarrangement, in bead form, and/or in monolith form.
 18. A method oftreating mainstream smoke of a smoking article of claim 13, bycontacting mainstream smoke with the porous composite, wherein theporous composite selectively removes at least one selected constituentfrom mainstream smoke.
 19. The method of claim 18, wherein said selectedconstituent removed is at least one of an aldehyde, ketone, hydrocarbon,aromatic, HCN, a nitrile, CO, a polar or non-polar organic compound ormixtures thereof.